The most effective Barching composition with wb comes from putting 4 wb and fill with barbs in 1st and 2nd barracks, then all arch in the 3rd and 4th barrack, this tends to give slightly more archers than barbs but not completely outweighing the barbs, 10 wall breakers probably takes up a bit too much troop space for a th7, considering the bases which you will tend to raid as a th7
I like to bam rather than barch in order to get the fastest possible army. Fill tow barracks with archers and two with barbs. Fill your dark barracks with minions and get attacking! It will start to get to be where there are more barbs than archers so either save archers at the end of attacks or after every few attacks put 3-7 archers before barbs in the barracks.
You have to experiment for what works best for YOU. Not what other people think
LAMO
If you use wb, you are not barching correctly. Been using barch since th1 and Im now Th9. 2 barracks each that's it! It's all about efficiency and how fast you can go to the next raid